Interesting article posted to my Google Scholar search (note it is in both Portuguese and English). Notable is this housing preference finding,

To study the behaviour of the common octopus (Octopus vulgaris) towards the traditional amphora clay shelter-pot, the cylindrical plastic shelter-pot and the new amphora plastic shelter-pot, several experiments were performed in controlled tanks. Three main questions were attempted to answer concerning the preferences of the common octopus towards the pots: 1) What kind of material: plastic or clay (traditional); 2) What shape: cylindrical or amphora (traditional); 3) What colour: white, black or red brick (traditional). The results showed no particular preference towards the material of the fishing The common octopus fishery in South Portugal: a new shelter-pot ÍNDICE 133 gear; a strong preference for the traditional amphora shape; and a strong preference for the black colour. Keywords: Octopus fishery; octopus shelter-pots; octopus fishing gear; octopus behaviour.